Minnesota Vikings quarterback Sam Bradford has been ruled out of Sunday's game against the Tampa Bay Buccaneers, and concerns about his knee injury have called into question his availability in the coming weeks.
Vikings coach Mike Zimmer confirmed on Friday afternoon that Bradford will again be unavailable, leaving Case Keenum to start a second consecutive game for Minnesota.
Asked if Bradford could be back for the October 1 meeting with the Detroit Lions, Zimmer said: "I don't know. I love you [reporters], but I don't have a crystal ball. All I know about is this week."
Bradford is reportedly seeking a second opinion on his left knee from Dr. James Andrews, who has previously operated on his knee and shoulder.
He was limited in practice on Wednesday and Thursday and did not appear on the practice field on Friday.
Keenum was 20 of 37 passing for 167 yards with no touchdowns or interceptions in Minnesota's loss to the Pittsburgh Steelers last Sunday. Kyle Sloter will back him up this weekend.